This invention relates generally to frequency synthesizers and more particularly to digital synthesizers adapted to produce radio frequency signals.
As is known in the art, one type of digital frequency synthesizer includes a plurality of highly stable oscillators coupled to a plurality of counters of frequency multipliers to produce subharmonic frequency signals. These signals are then selectively combined using mixers and filters to produce a signal having the desired frequency. Such apparatus is expensive and not generally suited to produce signals having relatively short time durations such as pulses used in radio and pulse communications systems.
Another type of a digital frequency synthesizer is described in my U.S. Pat. No. 4,240,034, issued Dec. 16, 1980 and assigned to the same assignee as the present invention. As described in my patent a digital frequency synthesizer is adapted to produce radio frequency signals having a predetermined frequency. While such frequency synthesizer is useful in many applications it is sometimes desired to provide a digital frequency synthesizer adapted to produce radio frequency signals having a frequency within an extremely wide band of frequencies.